System for controlling the sublimation of reactants

ABSTRACT

An apparatus and method improves heating of a solid precursor inside a sublimation vessel. In one embodiment, inert, thermally conductive elements are interspersed among units of solid precursor. For example the thermally conductive elements can comprise a powder, beads, rods, fibers, etc. In one arrangement, microwave energy can directly heat the thermally conductive elements.

REFERENCE TO RELATED APPLICATIONS

The present application claims the priority benefit under 35 U.S.C.§119(e) of Provisional Application No. 60/389,528, filed on Jun. 17,2002. The present application is also related to Provisional ApplicationNo. 60/400,210, filed on Jul. 30, 2002, and U.S. application Ser. No.10/629,029, filed on Jul. 29, 2003, entitled “An Improved SublimationBed Employing Carrier Gas Guidance Structures,” which claims priorityfrom Provisional Application No. 60/400,210.

FIELD OF THE INVENTION

The present invention is related to solid precursor sources used for thedeposition of thin films on substrates. More specifically, the presentinvention is related to the enhancement of thermal conductivity to thesolid precursor inside the precursor source apparatus.

BACKGROUND AND SUMMARY OF THE INVENTION

Quite often solid precursors are used for vapor reactants, becauseliquid or gaseous precursors for a certain element may not be readilyavailable or do not exist at all. Such solid precursors are useful in avariety of contexts, including, without limitation, atomic layerdeposition (ALD) and other semiconductor fabrication processes. However,it is more difficult to use solid precursors than liquid and gaseousprecursors.

Basically, the handling of solid precursors seems to be straightforward.Solid precursor is loaded into a container that is heated to asufficiently high temperature. The precursor sublimes and the precursorvapor is conducted to a reaction space where it is used for thedeposition of thin film on the substrate surface.

Precursor powder generally has rather poor thermal conductivity. Thethermal conductivity of the precursor bulk may be low and/or there maybe empty voids between the precursor particles with little contactsurface between the particles, which is undesirable for the conductionof heat energy through the precursor. The volume of the voids depends onthe packing density of the precursor powder. At low pressures, heattransport by convection is also generally inefficient, especially whenthe precursor volume consists of very small voids between the precursorparticles. Heat transport by radiation is also generally inefficientbecause the temperature differences are relatively small and theradiation view factor (line-of-sight paths available for radiantheating) for the bulk of the powder is essentially zero.

When the precursor vessel is heated from outside, the precursor may havea sufficiently high temperature near the vessel walls while the centerparts of the precursor powder are insufficiently heated. Thistemperature differential results from the long period of time requiredto heat the centrally located portions of the precursor powder in theprecursor vessel. In addition, sublimation of the non-centrally locatedprecursor consumes thermal energy, further contributing to the center ofthe precursor powder volume remaining at a lower temperature than thepowder proximate the vessel surfaces throughout the process. During ALDpulsing, this temperature differential can cause the solid source todemonstrate a poor recovery rate after using the precursor source for anextended period, because it becomes more and more difficult to reach anequilibrium state in the gas phase of the precursor vessel. Although ALDprocesses are relatively insensitive to small drifts in pulseconcentration, significant decreases in the recovery rate can causeproblems, such as less than full surface coverage of a semiconductorwafer (or other substrate) with the precursor molecules.

Temperature differences inside the precursor vessel lead to thesublimation of the precursor into the gas phase in hotter parts of thevessel volume and to the condensation of the precursor back to the solidphase in cooler parts of the vessel volume. Often the top surface of theprecursor seems to be cooler than the rest of the precursor. It has beenobserved that a hard and dense crust forms over the surface of theheated precursor over time, causing a pulse concentration drift in theprocess employing the vapor reactant (e.g. ALD). The crust limits thediffusion of precursor molecules from the bulk material to the surfaceand eventually into the gas phase. The result is a decrease in theobserved sublimation rate of the precursor. Initially, the solidprecursor source works well but later it is difficult to get a highenough flux of precursor molecules from the source into the reactionchamber, despite the fact that a significant amount of solid precursorremains in the precursor vessel.

Another consideration in sublimation vessel design is that prolongedpresence of heated corrosive precursors places heavy demands on thosematerials in contact with precursors in the precursor vessel.

The preferred embodiments of the invention provide means for improvingthe uniformity of the source temperature in the whole solid precursorvessel volume. In accordance with one aspect of the present invention,inert materials that have high thermal conductivity are mixed with thesolid precursor to improve the thermal conductivity through theprecursor. For example, the inert materials can comprise particles,fibers, rods, or other elements with high thermal conductivitydistributed through the precursor vessel and intermixed with precursorpowder.

In accordance with one embodiment of the invention, a method ofproducing a vapor from a solid precursor for processing a substrate isprovided, including placing solid units of precursor into a vessel andinterspersing a thermally conductive material through the precursor. Thethermally conductive material thereby preferably serves to conduct heatenergy throughout the units of precursor. A vapor is then formed throughapplying heat energy to both the thermally conductive material and thesolid units of precursor. In one embodiment, after vapor formation, thevapor is routed from the vessel to a reaction chamber and reacted todeposit a layer on a substrate.

In accordance with another embodiment, a substrate processing system isprovided for forming a vapor from a solid precursor by distributing heatthroughout the precursor. The provided system comprises a heatconducting vessel configured to hold units of solid precursor, thermallyconductive elements being interspersed with the units of solidprecursor. A heater is also provided for heating both the precursor andthe thermally conductive elements.

In accordance with yet another embodiment, a substrate processing systemfor forming a vapor from a solid precursor is provided. The systemincludes a vessel configured to hold units of solid precursor and amicrowave generator adjacent to the vessel. The generator is configuredto transmit heat energy in the form of microwave energy to effectuatethe heating of the precursor.

In accordance with a further embodiment, a mixture for producing a vaporused in substrate processing is provided. The mixture includes a batchof precursor for producing a substrate processing vapor and a pluralityof heat transmitting solid forms interspersed through the batch ofprecursor. The plurality of heat transmitting solid forms collectivelyincrease the thermal conductivity of the batch of precursor.

Advantageously, implementation of the preferred embodiments decreasescrust formation at the precursor surface and enhances the sublimation ofthe precursor. In addition, improving sublimation rate uniformity overthe operational life of the precursor batch decreases the amount ofunused precursor. Refilling of the precursor vessel is also needed lessoften due to more efficient material utilization. Another benefit of thepresent invention is the improvement of the thin film thicknessuniformity on substrates by processes employing vapor from the solidprecursor by encouraging rapid recovery of the partial pressure ofreactant in the gas phase of the vessel to a steady-state value (onesuch value is P⁰, the saturation vapor pressure of the material) frompulse-to-pulse.

For purposes of summarizing the invention and the advantages achievedover the prior art, certain objects and advantages of the invention havebeen described herein above. Of course, it is to be understood that notnecessarily all such objects or advantages may be achieved in accordancewith any particular embodiment of the invention. Thus, for example,those skilled in the art will recognize that the invention may beembodied or carried out in a manner that achieves or optimizes oneadvantage or group of advantages as taught herein without necessarilyachieving other objects or advantages as may be taught or suggestedherein.

All of these embodiments are intended to be within the scope of theinvention herein disclosed. These and other embodiments of the presentinvention will become readily apparent to those skilled in the art fromthe following detailed description of the preferred embodiments havingreference to the attached figures, the invention not being limited toany particular preferred embodiment(s) disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic overview of a precursor source apparatus inlinebetween a gas source and a reaction chamber.

FIG. 1B is a schematic side view of the precursor source apparatus ofFIG. 1A, constructed in accordance with a preferred embodiment.

FIG. 2 is a schematic, partially cut-away perspective view of theprecursor source apparatus of FIG. 1B, showing a precursor vessel insidea pressure chamber.

FIG. 3 is a schematic side view of a precursor vessel from the prior artwith crust formation at the upper surface of a volume of solidprecursor, with arrows showing the direction of heat flow.

FIG. 4 is a schematic top view of a vessel insert with thermallyconductive rods attached to a vessel base, constructed in accordancewith a preferred embodiment.

FIG. 5 is a schematic perspective view of the insert of FIG. 4.

FIG. 6 is a schematic side view of a precursor source apparatus havingthermally conductive units interspersed with the precursor, inaccordance with a preferred embodiment.

FIG. 7 is a schematic, partially cut-away perspective view of aprecursor source apparatus having an adjacent microwave unit, inaccordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1A, a precursor source apparatus 5 is shown inlinebetween a carrier gas source 4 and a reaction chamber 6 configured toaccommodate a substrate 8.

FIG. 1B shows a preferred embodiment of the precursor source apparatus 5for vaporizing a solid precursor, the resulting vapor to be employed insubstrate processing, having a pressure chamber 10, an inlet 12, anoutlet 14 and, preferably, an over-pressure relief valve 16. The inlet12 is preferably attached to a carrier gas source 4 (FIG. 1A) via afirst conduit 2, while the outlet 14 is preferably attached via a secondconduit 3 to the reaction chamber 6 (FIG. 1A).

FIG. 2 is a schematic, partially cut-away, perspective view of theprecursor source apparatus 5 of FIG. 1, showing an inner precursorvessel or crucible 20 inside the pressure chamber 10. The inner crucible20 located inside the pressure chamber 10 is used as a precursor vessel.The shape and dimensions of the crucible 20 are selected depending onthe volume available inside the temperature-controlled pressure chamber10. The material of the crucible 20 can comprise inert substances, suchas quartz glass or silicon carbide. In addition, a particle filter 22 ispreferably located on top of the crucible 20. In an alternativeembodiment, the particle filter is located on the vessel outlet 14 orsecond conduit 3. Porous crucible walls are employed in certainpreferred embodiments, the walls of the crucible acting as particlefilters as the precursor vapor diffuses through the walls.

FIG. 3 illustrates crust formation in the prior art, one of the problemsthat preferred embodiments of the present invention seek to address.FIG. 3 shows a schematic side view of the crucible 20 holding a volumeof solid precursor 32. A crust 34 tends to form at the upper surface ofthe solid precursor 32, with arrows 36 in FIG. 3 showing the directionof travel of heat which is applied to the crucible 20.

FIGS. 4 and 5 show still another preferred embodiment of the presentinvention. An insert 38 is configured to fit within the crucible 20(FIG. 2) or other vessel in which the solid precursor is to be held. Theinsert 38 is preferably selected to have good heat conductivity. Theinsert 38 includes heat conducting elements 40, here rods, which aremachined and attached to a vessel base 42. Preferably, heat flows alongprimary axis of the elements 40, then radially outward into thematerial, resulting in the whole precursor volume being heatedefficiently and uniformly. Therefore, because the elements 40 functionas conductors rather than resistive generators of thermal energy, theydo not form a portion of an electrical circuit, as illustrated in FIG.5. The elements 40 are preferably formed from, for example, SiC of thehighest purity and quality, since the elements 40 can be cleaned andre-used. In another embodiment, the heat conducting elements arepreferably made of the same material as the vessel, e.g., stainlesssteel. In the illustrated embodiment, the elements are formed fromSiC-coated graphite, but in other embodiments the elements are uncoated.In yet other embodiments the elements are formed from heat conductingsubstances other than SiC and graphite.

In accordance with one preferred embodiment, the insert 38 of FIGS. 4and 5 is machined and fitted into the precursor vessel 20. Precursor isthen poured into the vessel 20. In accordance with another embodiment aprecursor vessel 20 is first filled with precursor powder 32 and thenelements 40, shown in FIGS. 4 and 5 as inert, heat-conducting rods, arepushed through the precursor 32 so that the lower ends of the rods 40touch the bottom of the precursor vessel 20. In an alternate embodiment,the rods are attached to the base of the source container 10 and thesource container 10 is filled with the precursor powder 32. In yet otherarrangements, rods are each configured to be inserted independently ofone another. Preferably, the selected rod density is a function of theheat transfer properties of the solid (i.e. a solid which has poor heattransfer desirably is selected to have a higher density to lessen theheat transfer path).

In accordance with the embodiments shown in FIGS. 4 and 5, the rods 40can be located on the bottom plate 42. Preferably the rods 40 arearranged, for example, in a polar coordinate type layout, so that eachunit of the precursor 32 is located within a certain maximum distancefrom the rods 40 or the base plate 42. The number of vertical rods 40attached to a plate depends on the physical properties of the precursor32. More rods can be used if the heat transport through the precursor isvery poor.

In yet other alternate embodiments the thermally conductive elementsinterspersed with the precursor units can be formed from fixed elementssuch as, for example, rods, stacked screens, sieves, coils, plates, etc.These units or elements can include both porous and nonporousstructures. Preferably, these fixed units or elements are arranged so asto maximize the total amount of thermally conductive surfaces in contactwith precursor, while allowing vapor diffusion from the carrier gasinlet to the outlet. Precursor preferably diffuses through the mixtureof powder and thermally conductive elements. Preferably, the carrier gasconvectively transports the chemical in the upper portion of the vessel(or head space) from the inlet to the outlet.

FIG. 6 shows a preferred embodiment in which loose thermally conductiveelements 46 are mixed with precursor powder 32 inside the crucible 20.In certain preferred arrangements the conductive elements 46 are powderparticles, while in alternate arrangements the conductive elements 46can comprise larger loose elements, such as fibers, pieces, flakes,pellets, spheres, or rings, etc. The chemical catalyst industry useselements having similar geometry (beads, pellets, spheres, rings, etc),each being coated with a catalytic material, which would also provideappropriate geometric unit configurations in order to practice alternatearrangements of the present invention. These units or elements 46 caninclude both porous and nonporous structures. Preferably, these looseelements 46 are arranged so as to maximize the total amount of thermallyconductive surfaces in contact with precursor 32. In certain preferredembodiments the elements 46 are formed from an inert, thermallyconductive material, such as a ceramic, e.g., SiC. The shapes andmaterials from which these elements 46 can be formed is discussed ingreater detail below.

In an alternate embodiment, a plurality of conductive elements 46 areinterspersed with a batch of precursor to form a mixture. Preferably,the inclusion of heat transmitting solid forms collectively increasesthe thermal conductivity of the batch of precursor.

Referring to FIG. 7, another embodiment of the present invention isshown employing an energy emitter 48 adjacent to the crucible 20. SiC oranother inert, energy-absorbing material (not shown) is placed in theprecursor vessel, preferably in the illustrated vessel or crucible 20along with precursor material, so that the precursor (not shown) is inclose contact with the energy absorbing material. In one arrangement,the precursor vessel is also preferably transparent to the emittedenergy. The wavelength of the emitted energy is preferably in themicrowave range, although alternate arrangements of the embodimentsdisclosed herein employ other wavelengths of emitted energy.

In a preferred operation, microwaves heat the microwave-absorbingmaterial and heat flows from the heated material, which can be inaccordance with FIGS. 4 and 5 or 6, to the precursor. In otherarrangements, a crucible is employed inside a vessel, the crucibleitself absorbing microwave energy, thereby transmitting heat from thewalls of the crucible to the precursor. Generally precursors that arenormally used for the deposition of thin films do not absorb microwavesand, thus, cannot be directly heated with microwaves. However,substances such as SiC absorb microwaves, allowing SiC to heat uprapidly, thereby effectuating the desired uniform heating of theprecursor. Similarly, other combinations of energy-absorbing materialand energy sources operating at different wavelengths will beappreciated in view of the present disclosure. In still anotherarrangement, when the precursor material is capable of directlyabsorbing electromagnetic energy like microwaves, direct heating of theprecursor material is sufficient to effectuate the desired precursorvaporization, such that separate microwave absorbing material can beomitted.

In alternate arrangements of the aforementioned embodiments, it shouldbe understood that it is also possible to omit the inert crucible andload the precursor directly into the bottom of the pressure chamber 10;preferably, the pressure chamber 10 surfaces in contact with theprecursor are sufficiently inert. A particle filter is also preferablyplaced on top of the precursor powder or, in an alternate embodiment, inthe conduit (not shown in figures) between the precursor source andreaction chamber. In embodiments in which a crucible is employed, thecrucible can be formed to have porous walls to serve as a filter,thereby reducing the need for a separate particle filter. In accordancewith one preferred embodiment, heat conducting material is then mixedwith the precursor, while in another preferred embodiment a machinedinsert is placed into the chamber prior to, during, or after loading ofthe precursor into the chamber.

Size and Shape of the Inert Heat Conducting Material

Heat conducting material or thermally conductive elements can be used indifferent shapes, e.g., powders, fibers, irregular pieces and machinedpieces.

The grain size of inert powders is selected according to theapplication, as would be appreciated by the skilled artisan. Precursorsource vessels that do not include any particle filters shouldpreferably be filled with conductive, inert elements (e.g., SiC powder)that are coarse enough to prevent the dusting of the material. Precursorsource vessels equipped with a filter can be filled with a wide range ofconductor particle size; preferably the smallest particles are stoppedby the particle filter. One benefit of using small inert, conductiveparticles is that very small voids in the precursor powder can be filledand the packing density and the heat conductivity through the precursorvolume is increased. One goal of certain preferred embodiments is toprovide uniform and high heat conductivity through the precursor powder.

In accordance with a preferred embodiment, the mixture of conductiveelements and precursor has a heat conductivity lower than that of pureconductor material and higher than that of pure precursor. For example,inert heat conducting material is added to the solid precursor forming asolid mixture, so that there is preferably about 10-80% by volume ofheat conducting material in the precursor/conductor mixture and, morepreferably, about 30-60% by volume of heat conducting material in themixture. Re-use of the conductor, although possible, is a challenge,especially when the particle size of the conductor is very small.

In another embodiment, fibers of inert, conductive material, such ascarbides or carbon, are employed. Fibers preferably conduct heatefficiently along the fibers through the precursor volume and, also,donate heat to the precursor that is located near the fibers. The fibersare preferably cut into pieces that have a length of about 1-20 mm andare mixed with the aforementioned precursor. For example, suitable SiCfibers are sold, e.g., by Reade Advanced Materials, USA. The heatconducting fibers selected preferably distribute heat from the heater orthe precursor vessel walls to the precursor.

In accordance with yet another embodiment, machined pieces of inert,conductive material are used, thereby preferably allowing certainbenefits. By employing larger machined pieces, recovery of heatconducting material is relatively easy after use. In addition, the heatconducting material can be cleaned and reused many times. Accordingly,very high purity and expensive heat conducting material can be usedeconomically. Machined pieces can take the form of, for example, rodsand plates (as illustrated in FIGS. 4 and 5), or combinations of thoseshapes and a variety of other shapes, including, for example, screensmounted at various levels along the length of rods or other extensions.

One embodiment employs a combination of machined pieces and smaller heatconducting pieces. Machined pieces preferably effectuate long-distanceheat transport from the heater or heated walls of the precursor vesseldeep into the precursor volume, while loose heat conducting units (e.g.,beads, powder, fibers, etc.) are preferably mixed with the precursor toeffectuate the local distribution of heat to the precursor. In onearrangement, heat conducting material in the form of powder is employedin combination with heat conducting material in the form of fibers. Inanother arrangement, rods are employed in conjunction with a powderedheat conducting material. In view of the disclosure contained herein,the skilled artisan will readily recognize other combinations of heatconducting material forms and materials that would also be advantageous.

In selecting the added inert material that is used according to thepresent invention, good thermal conductivity is desirable. Inertmaterials for this purpose preferably have a thermal conductivity of atleast about 50 W/m*K, more preferably at least about 80 W/m*K, for theapplications presented in this patent application at room temperature,and most preferably have such high conductivity under the conditions ofuse.

Silicon Carbide

Silicon carbide (SiC) is employed in certain preferred embodiments toform the inert material which is added to the crucible or vessel. SiC isan extremely hard material that has high thermal conductivity,negligible vapor pressure and very good resistance against chemicals atelevated temperatures. According to Performance Materials, Inc., USA,the thermal conductivity of SiC is 250 W/m*K at room temperature andabout 120 W/m*K at 400° C. A wide range of SiC grades with differentpurities are commercially available. The color of silicon carbide (SiC)is known to correlate with its purity. According to Reade AdvancedMaterials, USA, black SiC has a purity of up to about 99.2%, dark greenSiC has a purity of about 99.5% and the purity of light green SiC isabout 99.7%. SiC is available in the form of powder, grit, crystals,granules, wafers, fibers, platelets, bars and arbitrary form pieces.Typical impurities in SiC that is produced from silica sand and coke areSiO₂, elemental Si, free C, and Fe₂O₃. Preferably, such impurities areminimized to decrease potential contamination of the process employingthe precursor. Accordingly, in a preferred embodiment, the inertconductive material is preferably greater than 99% pure.

A number of commercial sources of high purity SiC exist. For example,SiC of 99% purity is available from Atlantic Equipment Engineers, USA,in all grit sizes. Poco Graphite, Inc., USA, also produces very highpurity SiC with a Chemical Vapour Infiltration (CVI) method where puregraphite is contacted with silicon monoxide (SiO) vapor (Eq. 1). Theamount of impurities in SiC is in the ppm level.SiO(g)+2C→SiC+CO(g)  Eq. 1Cerac, Inc., USA, sells vacuum deposition grade (99.5%) SiC pieces thathave dimensions in the range of 3-12 mm.

Other Materials

A number of other suitable inert carbides are commercially available.The thermal conductivity of transition metal carbides is typically about50% lower than the thermal conductivity of SiC; the conductivity oftransitions metal carbides will often be sufficient to provide improvedsublimation. Atlantic Equipment Engineers, USA, sells powders oftungsten carbide (WC), vanadium carbide (VC), tantalum carbide (TaC),zirconium carbide (ZrC), hafnium carbide (HfC), molybdenum carbide(MoC), niobium carbide (NbC) and titanium carbide (TiC). The purity ofthe carbide powder is typically 99.8-99.9%. Such metal carbides may alsohave useful metal-carbon stoichiometries other than 1:1.

In addition, alternate carbides, such as boron carbides (e.g., B₄C) thathave sufficiently high thermal conductivity can also be employed; boroncarbides are preferably not used for applications that are sensitive toboron impurities.

Another suitably inert and conductive material is PocoFoam™,manufactured by Poco Graphite, USA, which is very light carbon foam andhas a thermal conductivity in the 100 to 150 W/m*K range.

Coated Materials

In selecting a material from which to form the heat conducting material,it is undesirable to utilize materials that have high heat conductivitybut have a property that, unmodified, prevents the direct use of thematerial in solid precursor vessels. For example, a potential materialmay have a desirable thermal conductivity, but the material reacts withthe precursor during processing, i.e., during sublimation. Therefore,the material which is chosen to directly contact the precursor ispreferably inert. Certain preferred embodiments allow the use ofmaterial that if used alone would be undesirable, by coating a non-inertmaterial having a high thermal conductivity with an inert substance. Forexample, both graphite and silicon are good conductors of heat. Graphiteis very soft and easily forms solid particles that may contaminatesubstrates in a reaction chamber. A hard inert coating is thuspreferably formed on the graphite surface to decrease the number ofparticles released from the graphite. Similarly, silicon is an efficientreducing agent if the native oxide on the silicon surface is broken. Aninert coating deposited on the silicon surface preferably prevents thereactions between the silicon and precursors.

In particular, graphite or silicon can, in certain preferredembodiments, be coated with SiC. Other suitable coating materials areboron carbides, niobium carbide (NbC), tantalum carbide (TaC), titaniumcarbide (TiC), tungsten carbide (WC), zirconium carbide (ZrC),molybdenum carbide (MoC), vanadium carbide (VC) and hafnium carbide(HfC). Such metal carbides may also have useful stoichiometries otherthan 1:1. In one embodiment, insufficiently pure carbides are preferablycoated with a thin, high-purity CVD carbide film that prevents thecontamination of the precursor in the precursor vessel. In thisembodiment, impurities of the CVD carbide coatings are in the parts permillion (ppm) range and, thus, do not significantly contaminateprecursors or substrates. Transition metal nitrides, such as niobiumnitride (NbN), tantalum nitride (TaN), titanium nitride (TiN), tungstennitride (WN), zirconium nitride (ZrN), molybdenum nitride (MoN),vanadium nitride (VN) and hafnium nitride (HfN), serve as furtherexamples of suitable inert coatings on heat conducting materials. Inaddition, in one embodiment, silicon nitride is formed on the siliconsurface and, thus, silicon parts and pieces are passivated.

The following examples, including the methods performed and resultsachieved are provided for illustrative purposes only and are not to beconstrued as limiting upon the present invention.

EXAMPLES Example 1

A Pulsar® 3000 ALCVD™ reactor, available commercially from ASMInternational, N.V. of Bilthoven, The Netherlands, was used for thedeposition of HfO₂ from alternating pulses of HfCl₄ and H₂O viasequential, self-saturating surface reactions. The HfCl₄ vapor for thosepulses was provided from a solid source. A mixture of 157.6 g of HfCl₄and 200.8 g of 99.5% SiC (obtained from Orkla Exolon, Norway) was loadedinto a source container. In the mixture there was approximately 100 cm³of each precursor. Thus, the mixture of precursor material andconductive elements was a 1:1 volumetric mixture.

As a result, the source temperature could be lowered from 200-205° C.(no carbide fill) to 180° C. (with carbide fill). It is believed thatthe recovery rate (i.e., time after pulsing that sufficient vapordevelops for the next pulse) of the source improved because of theincreased and more stable sublimation rate of the precursor. Thedeposition of thin films from the same precursor batch was made possiblefor a longer time than without the carbide fill. The addition of SiCimproved the HfO₂ thin film thickness uniformity on the substrates. Useof SiC conductive filler did not affect the number of particles onwafers.

Example 2

ZrCl₄ powder was mixed with boron carbide (B₄C) powder in a glove box.The mixture was loaded into a source boat made of glass. The source boatwith the mixture was then placed in a glass tube to serve as a carriertube. Ends of the tube were covered with Parafilm to prevent theexposure of ZrCl₄ to room air and moisture. The tube was carried fromthe glove box to an F120 ALD reactor from ASM International N.V., andthe source boat was moved from the carrier tube to a source tube(pressure vessel) of the reactor while inert nitrogen gas was flowingout of the source tube. After the loading of the source boat wascompleted and substrates were placed into the reaction chamber of thereactor, the reactor was evacuated to vacuum with a mechanical vacuumpump. Pressure of the reactor was adjusted to about 3-10 mbar withflowing inert nitrogen gas. The reaction chamber was heated to thedeposition temperature and the ZrCl₄ reactant zone of the reactor washeated also to the sublimation temperature. ZrO₂ thin film was depositedfrom sequential alternating pulses of ZrCl₄ and H₂O vapor. It was foundthat the sublimation rate of ZrCl₄ increased clearly when boron carbidehad been mixed with ZrCl₄. Boron carbide helped to transport heat energythrough the precursor volume.

Although this invention has been disclosed in the context of certainpreferred embodiments and examples, it will be understood by thoseskilled in the art that the present invention extends beyond thespecifically disclosed embodiments to other alternative embodimentsand/or uses of the invention and obvious modifications thereof. Thus, itis intended that the scope of the present invention herein disclosedshould not be limited by the particular disclosed embodiments describedabove, but should be determined only by a fair reading of the claimsthat follow.

1. A substrate processing system for forming a vapor from a solidprecursors by distributing heat to the precursor in a sealed container,the system comprising: a vessel configured to hold units of solidprecursor, the vessel including a base, a top portion opposite the base,and a sidewall extending from the top portion toward the base, thevessel having no heater therein; an inlet that introduces a carrier gasinto the vessel; an outlet that releases gas comprising the vapor fromthe solid precursor from the vessel; and a plurality of thermallyconductive protrusions extending from at least one of the vessel baseand the vessel sidewall, the thermally conductive protrusions positionedand dimensioned to extend through the units of solid precursor and toconduct heat generated by a heater external to the vessel from at leastone of the vessel base and the vessel sidewall to the units of solidprecursor when the vessel is loaded with the units of solid precursor,wherein the thermally conductive protrusions each have a top surfacethat is space apart from the vessel top portion, and wherein thethermally conductive protrusions do not form part of an electrical orfluid circuit.
 2. The system of claim 1, wherein the vessel is a heatconducting vessel.
 3. The system of claim 1, further including areaction chamber fluidly coupled to the vessel, the chamber beingconfigured to provide a suitable environment for the reaction of avapor, originating from the vessel, to deposit a layer on a substrate.4. The system of claim 3, wherein the reaction chamber is a chemicalvapor deposition chamber (CVD).
 5. The system of claim 3, wherein thereaction chamber is an atomic layer deposition chamber (ALD).
 6. Thesystem of claim 1, wherein the units of solid precursor are in powderform.
 7. The system of claim 1, wherein the thermally conductiveprotrusions are formed from a substance which is substantially inert toreactions within the vessel.
 8. The system of claim 1, wherein thethermally conductive protrusions have a coating which is substantiallyinert to reactions within the vessel.
 9. The system of claim 1, whereinthe sealed container is a vacuum chamber surrounding the vessel.
 10. Thesystem of claim 1, wherein the thermally conductive protrusions arerods.
 11. The system of claim 1, wherein the thermally conductiveprotrusions are attached to a removable base plate that forms part ofthe vessel base.
 12. The system of claim 11, wherein the thermallyconducive protrusions are each configured to be attached to the vesselbase independently of one another.
 13. The system of claim 1, whereinthe thermally conductive protrusions comprise carbon.
 14. The system ofclaim 13, wherein the thermally conductive protrusions comprise amaterial selected from the group consisting of: metal carbide,transition metal carbide, boron carbide, and silicon carbide (SiC). 15.The system of claim 1, wherein the thermally conductive protrusions havea thermal conductivity of at least about 50 W/m*K at room temperature.16. The system of claim 1, wherein the thermally conductive protrusionshave a thermal conductivity of at least about 80 W/m*K at roomtemperature.
 17. A system for producing in a sealed container a vaporused in substrate processing, the system comprising: a vessel having abase, a top portion opposite the base, and a sidewall extending from thetop portion toward the base, the vessel having no heater therein andconfigured to be heated by an external heater; a batch of precursor forproducing a substrate processing vapor, the batch of precursorpositioned within the vessel; and a plurality of elongate heattransmitting solid forms that extend from at least one of the vesselbase and the vessel sidewall, the elongate heat transmitting solid formsbeing interspersed through the batch of precursor and being configuredto conduct heat generated by the external heater from at least a portionof the vessel to the batch of precursor, wherein the plurality ofelongate heat transmitting solid forms each have a top surface that isspaced apart from the vessel top portion.
 18. The system of claim 17,wherein the plurality of elongate heat transmitting solid forms areformed from a material selected from a group consisting of metalcarbide, transition metal carbide, boron carbide, and silicon carbide.19. The system of claim 17, wherein the plurality of elongate heattransmitting solid forms are substantially inert with respect to desiredreactions employed in the substrate processing.
 20. The system of claim17, wherein the plurality of elongate heat transmitting solid forms arecoated with a substantially inert material with respect to desiredreactions employed in the substrate processing.
 21. The system of claim17, wherein the plurality of elongate heat transmitting solid forms areconfigured to conduct heat from the precursor proximate to edges of theprecursor batch to precursor substantially centrally located within theprecursor batch.
 22. The system of claim 17, wherein the vessel is thesealed container and is configured for loading units of solid precursordirectly into a bottom of the vessel.
 23. The system of claim 17,wherein the vessel is a crucible within the sealed container.
 24. Thesystem of claim 1, wherein the vessel is the sealed container and isconfigured for holding the units of solid precursor directly in a bottomof the vessel.
 25. The system of claim 17, wherein the vessel furthercomprises an inlet that introduces a carrier gas into the vessel and anoutlet that releases gas comprising the substrate processing vapor fromthe vessel.